1. Field of the Invention
The present invention relates to an optical disc device, and relates in particular to an optical disc device for differentiating among different types of optical discs.
2. Description of the Related Art
In recent years, optical discs, namely, compact discs (CDs), digital versatile discs (DVDs), which have greater recording capacity than CDs, and Blu-ray™ discs (BDs), which have greater recording capacity than DVDs, have come to enjoy widespread use.
DVD-compatible optical disc devices are typically configured to also be compatible with CDs, which have less recording capacity than DVDs. Likewise, BD-compatible optical disc devices are typically configured to also be compatible with CDs and DVDs, which have less recording capacity than BDs.
In optical disc devices such as the above, which are compatible with optical discs of several different types, because the setting conditions for playback and recording vary with the different types of optical disc, it is necessary to differentiate the type of an optical disc prior to playing back or recording onto the optical disc.
An optical disc device compatible at a minimum with CDs and DVDs typically differentiates between whether an optical disc is a CD or a DVD by the flow operation shown in FIG. 9.
However, in the case of DVD-RAM, due to the presence of a guard zone and complementary allocated pit addresses (CAPA), when a focus search is performed with a laser diode (LD) that emits an infrared laser in the 780 nm wavelength band (a CD laser), the focus error signal CDLD_FE and the focus sum signal CDLD-FS are extremely small, and the differentiation value A established in Step S20 is not highly accurate. For this reason, there have been cases in which a DVD is erroneously differentiated as a CD, through the determination made in Step S30 or Step S70.
Japanese Laid-open Patent Application 2009-54229, Japanese Patent No. 3890709, and Japanese Laid-open Patent Application 9-106617 disclose techniques for differentiating whether an optical disc is a CD or a DVD. However, in each of these techniques, the accuracy of the differentiation value A is not high, and therefore erroneous differentiation of a DVD as a CD is not prevented.